Big decisions make me nervous. I'm okay when it comes to ordering dinner or buying a new pair of jeans, but if I'm selecting a house, a job, or even a mate, some part of me always wonders whether I'm making the best choice.

It's not that I'm a slave to perfection (honest!). It's just that I'm simply trying to steer clear of future regrets and the anger, frustration, grief, and self-blame that accompany them and make regret such an unwelcome, energy-draining emotion.

In the dark, long days of winter, it's natural to spend time internally focused, looking back over our lives. Sifting through the past is how we find meaning, so we can enrich the days to come with greater wisdom and clarity. But sometimes this thought process turns on us, and regret takes on a life of its own, affecting our moods and health. (This is especially true for people with seasonal affective disorder, a common type of depression linked to low levels of light.)

Regret is one of the most felt but least discussed emotions. While directing a stress disorders clinic years ago, I became convinced that self-blame was one of the primary thought patterns that prevented emotional and even physical healing in my (mostly female) patients.Ruminating about how wrong or deficient you are (How could I have been so stupid? or What an idiot I am!) makes you feel small and ashamed. It pulls you out of the present and keeps you stuck in the past, destroys your peace of mind, and elevates the stress hormone cortisol. High cortisol levels, in turn, can undermine immunity, memory, metabolism, and even cardiac health.

The first step to understanding regret in your own life is to learn how it works. Cornell University psychologist Thomas Gilovich, PhD, says that regret comes in three emotional flavors:

Hot

Wistful

Despairing [pagebreak]

When the guy you've been dating turns out to be married (and in some remote corner of your mind you knew that), you're likely to experience regret as the "hot" emotions of anger, embarrassment, and irritation.

When you think about how fast your kids grew up and wish that you'd spent more time with them, your regrets will probably fall into the "wistful" category, where nostalgia and sentiment prevail. When you realize that you invested your pension with a con artist who skipped town, you may experience regret as helplessness and utter desperation.

Gilovich also found that short-term regret is stronger for actions you took (you bought a fabulous pair of shoes that cost a week's salary) than for inactions (you passed up those great shoes and wore your old ones to your best friend's wedding). Conversely, long-term regret is stronger for actions and opportunities that you passed up (that person you didn't date or the degree you never finished) than for actions you took.

Like any emotion, regret is a teacher—and the key is to get its message and then let the messenger go. Here are a few simple suggestions that can help you move on from the specific type of regret you feel.

When you're obsessing over what you didn't do, take action, if possible.

You can complete the degree you started 20 years ago, write a letter to someone with whom you have unfinished business, or realize the dream of moving to Alaska that you set aside when the kids were young.

On the other hand, Mr. Right, the man you passed over in your hurry to marry Mr. Wrong, may no longer be available. In that case, the best advice is: Let it go. And if it's really too late to repair the past, you can still come to peace with an error of omission by changing your attitude.

Social scientists have discovered that after we make a choice, we get more comfortable by rationalizing—bolstering it with what we consider to be good reasons. You can benefit from rationalizing inactions, too.

For years, whenever I had a twinge of regret about not acting fast enough to buy my dream house when it came up for sale on the cheap, I used a positive rationalization—I'm so happy living where I am now—that helped me decide that losing the house was indeed for the best. [pagebreak]

When you're obsessing over what you did, make amends.

Gilovich suggests three ways to minimize negative feelings over regrettable actions. The first is to undo or remediate them, if possible. So if you took the money you were planning to save this year and went to Europe instead, you can do financial penance and save twice as much next year. That should even the score a little.

The second method is to find a silver lining that makes the pain worthwhile. Your regret over marrying, and then divorcing, Mr. Wrong might be softened by knowing that you'll never again settle for less than you deserve.

The third key to reducing regret is called dissonance reduction. Dissonance is the difference between what you expected and what you got. Let's say that you bought an expensive new car, believing that it had a very comfortable ride. But in fact, the car is a poor ergonomic fit for you and gives you a backache. So what do you do?

Find something great about the car that makes it worth the money despite the fact that it's uncomfortable. Maybe it has a stellar safety record or a high resale value—or it just looks hot. By dwelling on its positive attributes, you reduce dissonance and adjust to having to put a pillow behind your back to get comfortable.

That kind of wisdom—applied to every area of your life—is the best way I know to keep regret outside in the cold, where it belongs.

Learn tips for fending off regret.

The things you didn't do are likely to cause the most regret. So when a great opportunity arises, consider gathering your courage, mobilizing your support systems, and going for it.

Perform a random act of kindness. It's a wonderful way to help you make up for something that you feel bad about but can't directly correct.

Be a thought transformer. When an old mental regret pops into your head, substitute a positive image of the future you hope to create.